Additive Effect of Water on the Decomposition of VOCs in Nonthermal Plasma

Catalytic nonthermal plasma reactor for the abatement of low concentrations of benzene

“…However, the product selectivity also depends on the water content in addition to VOC chemical structure. Some studies reported the optimal water vapor content for achieving the best VOC removal efficiency (Ricketts et al 2004;Sugasawa et al 2010: Karuppiah et al 2012). The effect of water vapor has been mostly studied with packed-bed DBD reactors for removal of benzene (Ogata et al 2000;Cal and Schluep 2001;Futamura et al 2002).…”

“…The abatement of VOCs under dilute concentrations (\1,000 ppm) may not be economical with conventional technologies such as adsorption on activated carbon, catalytic oxidation, and thermal oxidation (Subrahmanyam et al 2006a;Chorria et al 2007;Demeestere et al 2007;Zhu et al 2008: Li andGong 2010). NTP generated by electrical discharges under ambient conditions has specific advantages like mild operating conditions and may generate strong oxidizing agents like ozone, hydroxyl radical, H 2 O 2 , as well as UV light (Demeestere et al 2007;Demidyuk and Whitehead 2007;Magureanu et al 2008;Sugasawa et al 2010). However, by-products such as CO, CO 2 , and NO x seem unavoidable under operation of plasma reactors.…”

Methanol oxidation in dry and humid air by dielectric barrier discharge plasma combined with MnO2–CuO based catalysts

“…Moreover, the VOC conversion and ozone concentration were reduced at high humidity levels (level depending on plasma discharge type) due to the modification of the discharge electric field, leading to a decrease of reactive plasma volume and chemical species [14]. Regarding by-products selectivity, the affinity of formaldehyde to water would favor its direct transformation into CO2 at the expense of CO, according to Sugasawa [9]. The total oxidation of methyl formate and methylal under humid flow contributes to the improved CO2 selectivity.…”

“…One way, which has been developed extensively, to overcome these disadvantages is by placing a catalyst inside or post discharge. Depending on the VOC chemical structure, nonthermal plasma reactor layout and catalyst chemical nature, several conclusions were drawn in respect of VOC removal efficiency (RE), ozone concentration, carbon mass balance (CMB), by-products selectivites, specific energy or discharge behavior [4][5][6][7][8][9][10][11][12][13][14]. Treatment by non thermal plasma alone succeeds in removing low concentration pollutants at low energy consumption compared to conventional catalytic processes.…”

“…When a catalyst is combined to the plasma under humid conditions, in plasma or post plasma, a decrease of the VOC removal efficiency was observed, independently of reactor type or VOC chemical structure [5,6,[8][9][10][11]18]. The beneficial effect of the catalyst was hindered by surface coverage with water molecules thus limiting access to active sites [6,8,[18][19][20].…”